[flang][RFC] Change the interface for non-BIND(C) CPTR type with VALUE attribute

[peixin]

Summary

When the type(c_ptr/c_funptr) argument has value attribute in non-BIND(C)
procedure, it is passed by VALUE in gfortran. ifort does not do this. Be
consistent with gfortran.

Fix #58756.

[PeteSteinfeld]

Thanks, @peixin. I have verified that this builds and tests correctly and, in combination with the fix in https://reviews.llvm.org/D137237, fixes the problem that I reported in #58739.

@jeanPerier , can you please verify that the changes to the generated FIR look correct?

[jeanPerier]

LGTM

flang/lib/Lower/CallInterface.cpp

if (obj.attrs.test(Attrs::Allocatable) || obj.attrs.test(Attrs::Pointer)) {
       // Pass as fir.ref unless it's by VALUE and BIND(C). Also pass-by-value
       // for numerical/logical scalar without OPTIONAL so that the behavior is
       // consistent with gfortran/nvfortran.
       // TODO: pass-by-value for derived type is not supported yet
       mlir::Type passType = fir::ReferenceType::get(type);
       PassEntityBy passBy = PassEntityBy::BaseAddress;
       Property prop = Property::BaseAddress;
       if (isValueAttr) {
+        bool isBuiltinCptrType = fir::isa_builtin_cptr_type(type);
         if (isBindC || (!type.isa<fir::SequenceType>() &&
                         !obj.attrs.test(Attrs::Optional) &&
-                        dynamicType.category() !=
-                            Fortran::common::TypeCategory::Derived)) {
+                        (dynamicType.category() !=
+                             Fortran::common::TypeCategory::Derived ||
+                         isBuiltinCptrType))) {
           passBy = PassEntityBy::Value;
           prop = Property::Value;
-          if (fir::isa_builtin_cptr_type(type)) {
+          if (isBuiltinCptrType) {
             auto recTy = type.dyn_cast<fir::RecordType>();
             mlir::Type fieldTy = recTy.getTypeList()[0].second;
             passType = fir::ReferenceType::get(fieldTy);
           } else {
             passType = type;
           }
         } else {
           passBy = PassEntityBy::BaseAddressValueAttribute;

flang/test/Lower/call-by-value.f90

 ! CHECK:         fir.call @_QPinternal_call4(%[[VAL_3]]) : (!fir.boxchar<1>) -> ()
 ! CHECK:         return
 ! CHECK:       }
 
 subroutine test_char_value(x) bind(c)
   character(1), value :: x
   call internal_call4(x)
 end
+
+! CHECK-LABEL: func.func @_QPtest_cptr_value(
+! CHECK-SAME:                                %[[VAL_0:.*]]: !fir.ref<i64> {fir.bindc_name = "x"}) {
+! CHECK:         %[[VAL_1:.*]] = fir.alloca !fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>
+! CHECK:         %[[VAL_2:.*]] = fir.field_index __address, !fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>
+! CHECK:         %[[VAL_3:.*]] = fir.coordinate_of %[[VAL_1]], %[[VAL_2]] : (!fir.ref<!fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>>, !fir.field) -> !fir.ref<i64>
+! CHECK:         %[[VAL_4:.*]] = fir.convert %[[VAL_0]] : (!fir.ref<i64>) -> i64
+! CHECK:         fir.store %[[VAL_4]] to %[[VAL_3]] : !fir.ref<i64>
+! CHECK:         fir.call @_QPinternal_call5(%[[VAL_1]]) : (!fir.ref<!fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>>) -> ()
+! CHECK:         return
+! CHECK:       }
+
+subroutine test_cptr_value(x)
+  use iso_c_binding
+  type(c_ptr), value :: x
+  call internal_call5(x)
+end